Sequencing the survivors

Hebe de Bonafini (center), the head of Argentina's Mothers of Plaza de Mayo group, whose children disappeared during the "dirty"

By | September 1, 2007

<figcaption>Hebe de Bonafini (center), the head of Argentina's Mothers of Plaza de Mayo group, whose children disappeared during the " />
Hebe de Bonafini (center), the head of Argentina's Mothers of Plaza de Mayo group, whose children disappeared during the "dirty" war of 1970s, leads one of the marches in Buenos Aires's Plaza de Mayo in December 1979. Credit: AP Photo / Eduardo Di Baia

Twenty-five years ago, two Argentinean grandmothers flew thousands of kilometers to knock on the door of New York-based Argentinean geneticist Victor Penchaszadeh to ask him to reunite their broken families. A few years earlier, armed henchmen had burst into their children's homes and the homes of thousands of other Argentineans considered to be political dissidents, spiriting them away to secret detention centers. Many were never seen or heard from again.

One 1978 night, gunmen took Argentineans Claudio and Monica Logares and their 23-month-old child, Paula. Like hundreds of children either abducted with their parents or born to captive mothers, Paula grew up in the house of a government sympathizer (one of the guards at her parents' detention center), unaware of her own identity or the fate of her parents, who disappeared.

But Argentineans didn't forget about her, and the grandmothers resolved to restore their nation's families. "The question in 1982 was: 'What if we find someone? How will we know that it's our son or our daughter?'" remembers Penchaszadeh, who fled the country when the military took over in 1976. "They knew that they needed scientists."

In 1983, the military rule in Argentina was replaced by a democratic government, and scientists got to work. Because DNA sequencing technology was still under development, researchers turned to human leukocyte antigen (HLA) typing, widely used to match organ donors or determine paternity. If the parents are missing or dead, however, the calculation of relatedness becomes more complicated. "We simply had to develop some statistical maneuvering to deal with the fact that we didn't have the parents," says Penchaszadeh.

The task of developing a method that could use HLA typing fell to famed Stanford University geneticist Luca Cavalli-Sforza and University of California, Berkeley, geneticist Mary-Claire King. In 1984, King traveled to Buenos Aires as part of an AAAS delegation to help the human rights group, The Grandmothers of Plaza de Mayo, find their surviving kin. Working with Cavalli-Sforza and others, King developed the necessary statistical protocol and began identifying children. In 1985 the Argentine congress passed a law officially establishing a genetic bank and lab in Buenos Aires, along with the legal framework necessary for surviving children and relatives to come forward.

The passage of this law caused a public flood of families looking for disappeared children, King says. HLA typing, because of its limitations, identified only the handful of children with many grandparents still alive. King consulted her former PhD adviser, Allan Wilson, a geneticist at Berkeley, who told her about the great advances in PCR-aided mitochondrial DNA sequencing, which can match children with only one maternal relative. The sequencing work "very quickly focused on mitochondrial sequencing," which became the primary identification tool in 1986, says King.

This new approach changed everything. "In the HLA times, you had to run the test right away," because fresh blood samples yield the most reliable results, says Penchaszadeh. "When DNA [testing] came about, you could simply store a sample." And, error rates are "almost zero [since] you eliminate much of the observer error, and you don't need to resort to complicated statistical formulations to establish the probability of grandpaternity," says Penchaszadeh.

Now, more than 80 young Argentines have been reunited with their extended families, owing to use of the full panoply of genetic technologies including nuclear DNA markers. "It's a wonderful example of the use of genetic technology to foster human rights and to benefit mankind," says Penchaszadeh. "It's had a huge impact," says King. "I'm enormously proud of being involved in it." But there's more to do: King says about 160 Argentinean children who disappeared still remain in the database, unidentified and not reunited with their families.

Paula Logares was one of the fortunate children for whom HLA typing worked, and in 1984, the Supreme Court of Argentina reunited her with her biological family at the age of 8. Paula's surviving relatives told King about the day they nervously brought Paula to the home she had not seen since a toddler, unsure whether she would remember it. According to her family, Logares walked through the doorway, then immediately turned left, and headed straight for the room that used to be her nursery. Looking around, she asked: "Where is my teddy bear?"

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